Corrugated pipes are commonly used for drainage purposes. The following criteria should be addressed when designing a coupling device to be used for joining drainage pipes together: the coupling device's inner surface must be smooth and continuous so as to prevent debris from creating obstructions; the coupling should be water tight; the coupling device should be inexpensive to manufacture; and workers in the field should be capable of establishing the coupling with a minimum of effort.
Many coupling designs have attempted to achieve some of the above criteria. Earlier coupling designs relied primarily on bolts to couple corrugated pipes together. See, for example, U.S. Pat. No. 559,642, J.H. Watson, issued May 5, 1896; U.S. Pat. No. 897,416, J.H. Schlafly, issued Sep. 1, 1908; and U.S. Pat. No. 919,997, J. Zelch, issued Apr. 27, 1909. These designs proved unsatisfactory in providing a water tight seal and were frequently difficult to install.
A currently used coupling design involves the use of a corrugated metal band. The corrugated band of metal is positioned around the exterior of the joined pipe ends. Tightening bolts are used to secure the band into position. This coupling technique is labour intensive and time consuming to install.
Some recent coupling designs no longer rely primarily on the use of bolts to secure the coupling. In U.S. Pat. No. 4,913,473, E.G. Bonnema et al., issued Apr. 3, 1990, a plastic pipe with an inherent coupling device is disclosed. The plastic pipe is double-walled. The inner wall is cylindrical and smooth. The outer wall is corrugated with annular ribs. One end of the pipe functions as a male connector. The opposite end of the pipe functions as a female connector and has an enlarged sleeve moulded to its outer wall. The sleeve has a plurality of hinged latching members which are circumferentially spaced. When the male and female connectors are joined the latching members on the female connector engage the grooves between the annular ribs on the outer wall of the male connector. Once engaged, the pipes cannot be pulled apart unless the latching members are disengaged.
The Bonnema invention is restricted to double walled plastic pipes. Plastic pipes are not suitable for certain applications. Furthermore, the male and female connectors in the Bonnema invention are inherent to the pipe; consequently, the lengths of the pipes are dependent upon the manufacturing process.
In U.S. Pat. No. 4,222,594, H.J. Skinner, issued Sep. 16, 1980, a coupling device for joining corrugated pipes is disclosed. The coupling device is comprised of a male and female connector. At one end of the male connector there is at least one annular rib on its outer surface. A corresponding number of annular grooves are provided on the inner surface of one end of the female connector. The two connectors are coupled by inserting the male connector into the female connector at an angle and then swinging the male connector in line with the female connector.
A significant disadvantage of the Skinner coupling device is that it requires the worker in the field to perform many difficult physical manipulations in order to effect the coupling. First, the patent discloses that the male and female connectors must be connected, possibly screwed, to the ends of the pipes. Second, the male connector must be screwed into the female connector at an angle so that an annular rib is positioned in an annular groove. Third, the female connector must be maintained at a fixed position while the male connector is swung in line with the female component. Fourth, at the same time as the male connector is being swung in line with the female connector, the male connector must be pushed into the female connector. Clearly, the difficulty involved in performing these manipulations increases with the diameter and weight of the pipes to be joined. Furthermore, the coupling of a plurality of pipes using the Skinner coupling device is time consuming and requires excessive manpower.
The present invention uses a stab joint to couple the male and female connectors. Also, the connectors are made of a light weight material. Therefore, complex manipulations are not required to engage the connectors and the coupling of pipes can be performed relatively inexpensively and quickly by workers in the field. The coupling has an inner surface which is smooth and continuous; thereby, providing a conduit that will not impede the flow of fluids through coupled pipes. Furthermore, the coupling provides a liquid seal.
In addition, the present invention does not require that the pipes be cut to a predetermined length in order to effect coupling. The connectors may be used to join pipes of any sufficient length that allows the connectors to be securely connected to the pipes.